Rotary line switch



7 May 6, 1930.

J. E. OSTLIN ROTARY LINE SWITCH Original Filed June '7. 192

lmrenluz" 1,; Jphn Elhs U s'TZms Application filed June 7, 1926, Serial no;

Patented May 6, 1930 nnrrsn STATES, PATENT OFFICE JOHN nosTLINn, on LIVERPOOL, ENGLAND, ASSIGNOR To AUTOMATIC ELEoTnIo Inc, or cIIIo eo, ILLINOIS, A CORPORATION OF DELAWARE ROTARY LINE SWITCH The present invention relates to improvements in or relating to switches as used in telephone systems and more particularly concerns that type otswitch known as a rotary line switch, that is to say, a line switch which is individual to each subscribers line and is of the type which has a continuously forward step-by-step movement and is advanced to a normal position after use. In switches of this type it is necessary to provide means to ensure that the cut-otfrelay, which connects the conductors leading from the subscribers station to an outgoing trunk, cannot be operated after the subscriber has hung up and the switch is returning to normal until the normal position is reached. It has been proposed to do this byproviding an earth connection on the side of the cut-ofi relay which is not connected to the test lead or private normal coming from the connector banks. 7 Q 1 I Now when a connector makes connection with a rotary line switch,.it initially performs a testing operation over this private normal by connecting battery through a busy relay to the private normal. Consequently, when an earth connection is provided on the side of the cut-off relay which is not connected to the test lead or private normal coming from the connector banks, a condition which occurs when the rotary line switchis restoring to normal, andprovidedthebusy relay is oil? a sufiiciently high resistance compared with'the resistance ofthe cut-oil relay, the cut-off relay will not energize. The busy relay is, however,

arranged to operate in this circuit. However, in certain conditions itis neither convenient nor desirable to provide a test relay of speciallyhigh resistance, particularly in a rotary connector, and it is the object of the present invention to effectually prevent the cut-OE rela ener izin under an conditions which i b b i may occur in the connector. According to the present invention this may be efiected in two tion is the private normal free from an earth 114,189, and in Great Britain se tember zs, 19 25. Renewed December 6, 1928.

connection and then only if thesub'scriber,

whose line the line switch is associated with, is not initiating a call, that is to say, if he has not just lifted his receiver. By this means the line would always test busy to a connector switch until the rdtary line switch had resumed its normal position. V

The other alternative is to provide an open connection in the circuit of the private normal and the cut-oflf relay so that the private normal is disconnected from either battery or earth connection at the rotary line switch side,

while the'rotary line switch is returning to normal. V

One advantage ofthis latter arrangement receive the busy signal, but the connector reand he isready. to receive another call, the ,short interval whichelapsesbefore the call is that a subscriber calling a line does, not

mains on the line and switches through immediately the rotary line switch has reached is switched through is negligible; For this reason the invention has been solved in the 'two manners;

.In order that the invention may be more clearly understood and readily carried into effect a detailed descriptionof a rotary lineto the homing bank, theldesiredresult being obtained by circuit arrangements.

Fig. 3] shows a modificatlon of thearrangement according to Fig. 1, in which the circuits are arranged to prevent the meter from operating, should the line relay be operated manually during the time the cut-0E relay is energized.

A detailed description will'firstbe given of the arrangement'elwwll in Fig. 3 In this figure and in Fig. 1 the construction of the bank contacts are modified. Normally the number of bank contacts provided per set are 5, four with individual contacts for each position, one for the meter, two for the speaking conductors and the other for test sulated so that the total thickness of plates and insulation is approximately the same as for ,a single plate. One of these plates is earthed as hitherto, while the other plate is connected to a lead extending over the bank contacts ofthe cut-off and line relays to the rotary magnet. hen the switch is in an OK normal position, these two plates are bridged together by a single Wiper;

hen a call is initiated, line relay L is energized overqthe subscribers negative and positive speaking conductors and operates its armatures X and Y, armature X being arranged to make contact before Y and to connect one side of the driving magnet to the test wiper P. Armature Y connects earth to one side of the switching relay K and also to the private normal wiper PN as well as wiper The .connect'ionof earth-"potential to Wiper PN guards the .test conductor Pf since the bank .contacts engaged by wipers P and PN in home position are strapped together and complete an energizing circuit for the driving magnet DM which accordingly energizes and Ide-energizes to advance the wipers from home position into engagement with the next set of bank contacts.

iis'soon as wiper PN advances from home position, it bridges the earth plate EP and the homing plate HP together. The income ingtest conductor P is now guarded and remains guardedall'the time the switch is in an off-normal position .over wiper PN from the .earthed plate If the contact engaged Zby wiper P 'isidle, switching relay will energize in series with the driving magnet DM and switch the talking conductors .tliroughto the selected line. i 7

Assuming however that the firstset of bank contacts engaged by the wipers are busy, there will be an earth potential on the contact engaged by wiper P which will short circuit relay and complete an energizing circuit for magnet DM which will as before energize and de-energiize to advance the wipers to a fresh set of bank contacts. This operation will continue until an idle set of bank contacts is found whereuponsw-itching relay K energizes. Switching relay K, upon energizing, connects the negative and positive speaking conductors through'to the'negative and positive w ipersand disconnects the energiz'ing circuit for relay L at armatures K and K Relay L being slow to release does not fall away at once and relay K is held energized over armature Y. When the line and release relays of the selected switch energize, the latte'r relay connects earth to the bank contactengaged by wiper P and this earth potential serves to hold relay K energized over armature K after relay L deenergizes, as it will shortly after the opening'of its energizing circuit.

Relay K, at armature K opens a point in the homing circuit of magnet DM and prepares a circuit for the meter M. Relay L, upon de-energizing, removes earth potential at armature Y from the contacts engaged by wipers P and PN in home position, and

armature X prepares a point in the homing circuit. The meter M is operated in series with the driving magnet DM when .earth po- V tential is connected to the contact engaged by wiper M and upon energizing operates and closes a locking circuit for itself.

It will be seen that should an attendant operate relay L manually at a time when relay K is in operated positionthat such operation will have no effect upon the meter M. The switch is released when earth potential is removed from the contact engaged by wiper P which brings about the de energization of relay With relay K and relay L in deenergized' position the following circuit is completed for drivin magnet DM battery, driving magnet Dl\ and its interrupter contacts, K and its back contact, armature X and its back contact, homing plate HP, wiper'PN, earth plate EP. This circuit persists .until the wiper PN reaches home position, when the connection with the earth platerEP and'zt-he home plate HP is broken. y 7 It will be seen thatduring the time that the switch is returning .to normal, test conon the test wiper of the connector, conductor P, wiper PN in home position, winding of relay K, interrupter contacts and driving magnet DM to battery. Relay K alone ener-' gizes in this circuit and disconnects the normal battery and earth potentials from the negative and positive speaking conductors.

Referring to Figure 1, the private normal PN is connected to the homing wiper H through the first contact 1. The rotary line switch begins to rotate in the usual way due to the completion of a circuit from the private wiperP over contact 2, contact 3, rotary magnet DM to battery, The starting earth is so that when the line relay picks up, it is iearthed received over contacts 4 and 5. The advance of the switch is then automatic until the private wiper P fails to receive earth back, whereupon the cut off relay K energizes in known manner. As soon as the first step is made, the private normal receives an earth permanently from the lower plate LP.

It will be seen that when the calling party hangs up at the end of a conversation, the privatenormal PN remains earthed from the lower plate LP, and when relay K deenergizes, due to guarding potential being removed from test wiper P by the switch ahead, the following circuit'is completed for the driving magnet: earth, plateLP, wiper H, plate HP, contact 6, contact 7, interrupter contacts rotary magnet DM to battery. The rotary magnet now rotates automatically due to the homing plate HP bein linked tothe lower plate LP by the wiper The rotary magnet therefore rotates automatically until the wiper H reaches the home contact 1. It willthus be appreciatedthat by this means the private normal iseifectively earthed all the time the rotary line switch is returning to normal, and in fact all the time that the rotary line switch is off normal. I 7

Referring now to Fig. 2, this arrangement involves no modification of the contact bank as in Figs. 1 and 3. In this case, a slight modification is made to the meter leads, the meter being normally connected to earth when the cut-0E relay is de-energized, thereby giving a very rellable assurance that the 'meter cannot beoperated falsely. For this purpose the normal connection from the private normal PN may be traced as follows: PN, cut off relay K, contact 1, wiper H, contact 7, rotary magnet DM to battery. If however the switch is in the off-normal position, the completion of the circuit for the cut-off relay is dependent upon the energiza- 7 tion of either the line relay over contact 8 or the cut-off relay over contact 9.- Consequently, if the cut-off relay de-energizesand the switch is in an off-normal position and the line relay is also de-energized the circuit of the relay K is opened at the points 9, 8,

and 1 and therefore the private normal is dis connected, and no circuit canbe completed thereover until the switch returns to normal, when a circuit over contact 1 is completed. 'Earth is only connected to the common plate GP engaged by the homing wiper H 'when the cut-off relay de-energizes. Consequently,

one terminal of the meter is normally earthed;

Other modifications will readily occur to those versed in the art, for instance, as an alternative to the first case, off-normal springs may be provided instead of the plates or the homing wiper may be divided into two components, while as ail-alternative to the other case other circuits will readily occur to those versed in the art, but it is believed that the circuit shown is the one requiring the least number of' contacts additional to forrendering said cut-ofi' relay inoperable thereover whenever said switch is ofi-normal.

,2. In a telephone system, a rotary line switch of the homing type, a cut-off relay and a'line relay. in said switch, a bank comprising two insulated sections, a wiper for said switch for bridging said sections whenever said switch is off-normal, a driving magnet, and a homing circuit for saidmagnet including said Wiper, said two insulated sections, contacts on said cut-off relay, and contacts on said line relay in series. I p

3. In a telephone system, a homing type rotary line switch, an incoming test conductor for-, said switch, and a wiper for placing on said conductor an idle test'potential when said. switch is in normal position and a busy' test potential whenever said switch is off nor mal.

4. In av telephone system, a rotary linefor said line switch, a-bank contact; normally connected to said'switching relay, a magnet for operating said line switch to an off-normal position, an incoming test conductor, a

wiper for said switch adapted to place ground potential on said conductor and; said contact whenever said switch is in an offnormal position, and a circuit including said wiper for operating said magnet to return said switch to home position.

6. In a selector switch having a home position, two wipers insulated from each other, a circuit including one of said wipers for starting said switch, a circuit including the other of said wipers for restoring saidswitch, and a circuit including one of said wipers for marking said switch engaged whenever 'said switch is not in home position.

7.111 a selector switchhaving a normal'position, two wipers insulated from each other, means includingone of said wipers for start ing said switchand for testing trunk lines accessible to said switch, and means including the other of said wipers for restoring said switch and for marking said switch engaged whenever said switch is in an off-normal position.

8. In a telephone system, arotary line switch of the homing type, means for causing the rotary movement of the switch, an incoming test conductor, a wiper terminating said conductor, a home position contact therefor, and a cut off relay-controlled over the incoming test conductor, the wiper and the home position contacts simultaneously.

9. In a telephone system, a rotary line switch ofthe homing.type,.a cut oli" relay permanently connected to a bank contact, an incoming test conductor, and a circuit including the incoming test conductor and a wiper of the swltch in series for operating the cut ff re1ay.-

10. 'Inia telephone system, a rotary line switch of the homing type, a cut off relay, an

incoming test conductor, and a circuit including the incoming test conductor and a wiper of 'the switch in series for operating the cut off relay, the said switch wiper constituting means for preventing theoperation of the cut 0E relay when the switch is returning to the home position.

11. In a rotary line switch of the homing type, a cut ofi relay, an incoming test conductor, a wiper, a circuit for energizing said relay established under certain conditions and extending through said test conductor and said wiper when the wiper is in the home po sition, and a circuit for energizing said relay established under other conditions and excluding said wiper. 5 1

12. In a rotary line switch, a cutofi" relay, two wipers, and two circuits for operating said relay, each extending through a differentone of said wipers. 13. In a rotary line switch, a out OK relay,

two wipers, two circuits for operating said relay, each extending through a different one of said wipers, and a third circuit for operating said relay excluding both of said wipers. 14, In a rotary line switch of the homing type, a out 01f relay, an operating circuit and a holding circuit for said out oii relay closed successively during the establishment of an outgoing call, a third circuit for said cut off relay completed during the establishment of an incoming call, and means foropening said third circuit whenever said switch is in an off-normal pos t o V .15.. In. e ephone system, a i e, a ry line switch for said line, acut-ofi' relay in said switch, a circuit including a'wiper of said switch for energizing said relay on incoming calls .to said line, and means fordisconnecting said relay from said wiper wheneversaid switch is ottenonmal.

16. In a telephone -system,.a line, a rotary linesw-itch for said line, a cut-off relay in said switch, a home position contact-in the switch-hank of said switch permanently con.- nected to said relay, a wiper normally engaging-said contact, and a circuit including said wiper and said contact in series for energize ing said relay on incoming calls 'to said line.

17.'In an automatic hunting-switch, two wipers, two home position bank contactsellgaged by said'wipers, respectively, a conductor connecting said bank contacts, and a circuit including said conductor andsaid wipers for starting the hunting movement-0f, the switch. v 5

18. In a rotary line-switch ofthe homing type, a line relay, two wipers,p.an incoming test conductor, a stepping magnet, and .GQH- tacts on said line relaytorcmmectinga source of current through one of said wipers to said conductor :to make a the switch busy and through the otherot said wipers to s id Si agnet to cause the operation ther'eoi.

19. In an automatic switch, a wipena con? ductor terminating therein, two banl; contacts engaged by said wiper simultaneously, a circuit extending through said conductor,- said Wiper and oneo-fsaid bank contacts, and another circuit extending through said wiper and both bank contacts butnot through said conductor. i

20. In a homing type rotary line switch, a wiper, an incoming test conductor permanently connected to said wiper, and a cut-ofi relay energized over said conductor and wiper in series. 7

21. In a homing type rotary line switch, a

wiper, an incoming test conductor terminatmg in said wiper, and a cut-off relayconnected toa bank contact normally engaged by said wiper but disengaged therefrom whenever the switch is ofi-normal.

22. In a homing type rotary linesw-itch, a wiper, an incoming test conductor terminating in saidv wiper, a cut-off relay normally connected to said conductor throughsaid wiper but disconnected therefrom whenever the switch is off-normal, and a permanently grounded bank contact engaged by said wiper whenever said switch is off-normal.

23. In a rotary line switch of the homing type, a cut-0H relay, an incoming ,test conductor, a wiper, a circuit extending throughsaid test conductor and said wiper for energizing said relay in incoming calls, and a circuit excluding said wiper for energizing said relay in outgoing calls.

In witness whereof, I hereunto subscribe 1-25 my name this 19th day of May A. D. 1926.

, JOHN E. OSTLINE. 

